1. Field of the Invention
The present invention relates to a roll for a roll stand including a roll shaft with at least one roll ring mounted on the roll shaft, wherein the roll shaft is axially displaceable. The roll stand for rolling a metal strip may be, for example, a two-high stand, a four-high stand or six-high stand.
2. Description of the Related Art
When manufacturing a metal strip, the thickness and cross-section thereof are determined by the roll gap. The precise contour of the roll gap adjusted under load is dependent on various variables. These variables are the wear of the work rolls, the elastic deformation of the roll systems, the roll camber, as well as the thermal crown which is due to a non-uniform heating of the roll body between the center of the body and the edge of the body. Without making corrections by means of adjusting units, the crown of the work rolls continuously increases with increasing throughput of the rolling stock, and because of the thermal crown which changes in this manner the roll contour increasingly deviates from the desired contour, for example, a parabola.
In order to influence the deviation of the actual profile shape from the desired profile shape of the rolled strip during the rolling procedure, it is known in the art to construct single-piece work rolls or pairs of intermediate rolls in such a way that the roll body has a curved contour which deviates from a straight line extending parallel to the roll shaft, wherein this curved contour extends over the entire length of the roll body, and wherein the rolls are axially displaceable in opposite directions as disclosed in DE 30 38 865 C1. Consequently, the change of the thermal crown and the wear of the work rolls is compensated in such a way that the thermal crown is equal to the desired contour. In this connection, the roll gap is influenced by the curved contour of the roll bodies together with a relative displacement of the cooperating rolls.
In a roll of the above-described type disclosed in U.S. Pat. No. 4,407,151, the support load is influenced by an axial displacement of the roll shaft or support shaft.
Moreover, various systems are known in the art in which the crown of a roll, and also the support width in individual cases when the roll is used as a back-up roll, can be changed by means of hydraulic measures. In these systems, such as Nipco roll, VC roll, Sumitomo roll, inflatable roll, etc., the external shape or crown of the rolls and possibly also the resiliency of the roll relative to external loads along the roll body are changed by means of oil pressure cushions and/or hydraulically actuated support shoes and, thus, are adjusted to the rolling conditions.
The above-described embodiments have the disadvantage that the hydraulic system is complicated and, therefore, not very reliable in its operation. In addition, since the tightness of a roll is usually not sufficient, a contamination of the rolling oil or rolling emulsion by the hydraulic oil cannot be prevented.